Hydromulching for reducing runoff and soil erosion [Portugal]


technologies_1299 - Portugal

Completeness: 73%

1. General information

1.2 Contact details of resource persons and institutions involved in the assessment and documentation of the Technology

Key resource person(s)

SLM specialist:
SLM specialist:
SLM specialist:
SLM specialist:

Keizer Jan Jacob

Centre for Environmental and Marine Studies (CESAM) - Department of Environment and Planning-University of Aveiro


Name of project which facilitated the documentation/ evaluation of the Technology (if relevant)
Catastrophic shifts in drylands (EU-CASCADE)
Name of project which facilitated the documentation/ evaluation of the Technology (if relevant)
Preventing and Remediating degradation of soils in Europe through Land Care (EU-RECARE )
Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)
Fundação para a Ciência e a Tecnologia (FCT) - Portugal
Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)
University of Aveiro (University of Aveiro) - Portugal

1.3 Conditions regarding the use of data documented through WOCAT

The compiler and key resource person(s) accept the conditions regarding the use of data documented through WOCAT:


2. Description of the SLM Technology

2.1 Short description of the Technology

Definition of the Technology:

Hydromulch is spread immediately after a wildfire in order to reduce overland flow and prevent soil erosion.

2.2 Detailed description of the Technology


The research team of the University of Aveiro in collaboration with the fire Brigade and a private company applied the hydromulch in a burnt pine area burnt at moderate fire severity. Hydromulch was spreaded manually from a jet hose over a group of erosion plots, and both runoff and erosion were compared to an untreated group of plots.
The hydromulch was applied at a ratio of 3.5 Mg ha-1 providing an initial ground cover of 80%, and was found to reduce post-fire runoff in 70% and soil erosion in 83%.

Purpose of the Technology: Hydromulch has been particularly useful on steep slopes and strongly modified areas such as quarries, construction sites, and cut and fill slopes along roads (Robichaud et al., 2010). The hydromulch is a complex mixture which contain basically water and wood or paper fibers. Additionally it can contain seeds, surfactants, seed-growing biostimulants, nutrients and a green colorant. It is intended that each component affected some of the pieces of the post-fire runoff erosion process.
The high effectiveness in runoff reduction could be related to the effect of the wood fibers, because it increases the surface water storage capacity, but also due to the effect of the surfactants, a wetting agent that reduces SWR and increases soil infiltration. Ideally, post-fire hydromulching must be carried out immediately after the fire, over bare, unprotected and steep burnt areas. It is intended for places in which burnt severity was moderate to high and where there are very important values at risk, such as water reservoirs, populations, industries, human and wild life.

Establishment / maintenance activities and inputs: The hydromulch is applied once, immediately after the wildfire, aerially, from a tractor or also manually by using a jet hose operated by a person on foot. It basically consisted of a mixture of water, wood fibers and seeds. The seed composition should include autoctonous plant species, in order to avoid alien species into the burnt area and increase the germination success. Besides the composition, the application technique can influence the hydromulch effectiveness. Rough (2007) and Robichaud et al. (2010) reported that the hydromulch sprayed from vehicles was intercepted by the standing trees, and they recommended special caution when applying the mixture in areas with a high density of dead trees and from long distances. Aerial hydromulch can be a better and less expensive option, but Hubbert et al. (2012) checked that the intended application rates of 50% and 100% hydromulch cover resulted in only 20–26% and 56%.

Natural / human environment: The natural forest in central Portugal has been substituted by pine and eucalypt trees that are typically planted as monocultures for wood and paper pulp production. The landscape reflects a long history of intense land management, with a mosaic of (semi-) natural and man-made agricultural and afforested lands. In recent years, however, wildfires have increased dramatically in frequency and extent, and have been associated to soil fertility losses, and consequently to socio-economic losses.

2.3 Photos of the Technology

2.5 Country/ region/ locations where the Technology has been applied and which are covered by this assessment



Region/ State/ Province:


Further specification of location:


Specify the spread of the Technology:
  • evenly spread over an area
If precise area is not known, indicate approximate area covered:
  • < 0.1 km2 (10 ha)

Plot experiments

2.6 Date of implementation

If precise year is not known, indicate approximate date:
  • 10-50 years ago

2.7 Introduction of the Technology

Specify how the Technology was introduced:
  • during experiments/ research
Comments (type of project, etc.):

Hydromulch has been particularly useful on steep slopes and strongly modified areas such as quarries, construction sites, and cut and fill slopes along roads (Emanual, 1976; Benik et al., 2003; Robichaud et al., 2010).

3. Classification of the SLM Technology

3.2 Current land use type(s) where the Technology is applied

Forest/ woodlands

Forest/ woodlands

  • Tree plantation, afforestation
Products and services:
  • Timber
  • Fuelwood

Major land use problems (compiler’s opinion): Increased runoff and soil erosion, resulting in a decrease of on-site fertility and derived off-site effects such as loss of water quality, reservoirs water volume storage, higher risk of flooding and human beings damage.
Major land use problems (land users’ perception): Loss of wood resources and productivity.
Plantation forestry: Yes
Forest products and services: timber, fuelwood
Constraints of infrastructure network (roads, railways, pipe lines, power lines): price

Number of growing seasons per year: 1
Longest growing period in days: 270Longest growing period from month to month: September to May

3.5 SLM group to which the Technology belongs

  • improved ground/ vegetation cover

3.6 SLM measures comprising the Technology

agronomic measures

agronomic measures

  • A3: Soil surface treatment

Main measures: agronomic measures

Type of agronomic measures: mulching

3.7 Main types of land degradation addressed by the Technology

soil erosion by water

soil erosion by water

  • Wt: loss of topsoil/ surface erosion
  • Wg: gully erosion/ gullying
  • Wo: offsite degradation effects
physical soil deterioration

physical soil deterioration

  • Pk: slaking and crusting

Main type of degradation addressed: Wt: loss of topsoil / surface erosion

Secondary types of degradation addressed: Wg: gully erosion / gullying, Wo: offsite degradation effects, Pk: sealing and crusting

Main causes of degradation: deforestation / removal of natural vegetation (incl. forest fires) (Monoculture of forest plantations prone to forest fires)

3.8 Prevention, reduction, or restoration of land degradation

Specify the goal of the Technology with regard to land degradation:
  • reduce land degradation

Main goals: mitigation / reduction of land degradation

4. Technical specifications, implementation activities, inputs, and costs

4.1 Technical drawing of the Technology

Technical specifications (related to technical drawing):

Hydromulch should be spread as homogeneous as possible over steep areas (higher than 15º) burnt at high fire severity (represented in green and 1). Other areas which are flat (2) and burnt at low severity or only partially burnt (3) must be avoided.

Technical knowledge required for field staff / advisors: moderate

Technical knowledge required for land users: high

Main technical functions: control of raindrop splash, control of dispersed runoff: impede / retard, control of concentrated runoff: impede / retard, improvement of ground cover, increase in nutrient availability (supply, recycling,…), sediment retention / trapping, sediment harvesting

Secondary technical functions: control of dispersed runoff: retain / trap, control of concentrated runoff: retain / trap, increase of surface roughness, improvement of surface structure (crusting, sealing), increase of infiltration, increase / maintain water stored in soil

Material/ species: water-based mixture of organic fibers and green colorant
Quantity/ density: 3.5Mg ha-1
Remarks: achieve a ground cover of 80%

4.2 General information regarding the calculation of inputs and costs

other/ national currency (specify):


If relevant, indicate exchange rate from USD to local currency (e.g. 1 USD = 79.9 Brazilian Real): 1 USD =:


Indicate average wage cost of hired labour per day:


4.3 Establishment activities

Activity Timing (season)
1. Apply hydromulch
2. Trasportation (Track with a jet-spreading system)
3. Other

4.4 Costs and inputs needed for establishment

Specify input Unit Quantity Costs per Unit Total costs per input % of costs borne by land users
Labour Labour ha 1.0 128.2 128.2 100.0
Equipment Machine use ha 1.0 128.2 128.2 100.0
Other Hydromulch ha 1.0 3205.0 3205.0 100.0
Other Others ha 1.0 128.2 128.2 100.0
Total costs for establishment of the Technology 3589.6
Total costs for establishment of the Technology in USD 4602.05

Duration of establishment phase: 0.1 month(s)
Lifespan of the hydromulch: 1 year

4.6 Costs and inputs needed for maintenance/ recurrent activities (per year)


The prices were determined in winter 2009 for central Portugal. In other regions and for other formulations these prices can vary. When compared with straw mulch its price is extremely high, but despite this greater expense, hydromulching has been used especially in the USA after some fires when access was difficult, the slopes were too steep or subject to wind to use straw mulch and when there were particularly important ‘values at risk’, such as water reservoirs, cultural or natural heritage sites, national or regional wildlife protected areas or industrial plants

4.7 Most important factors affecting the costs

Describe the most determinate factors affecting the costs:

Accessibility and steepness will raise the costs, but selecting hydromulchings is also a main factor. The more complex the hydromulch the more expensive the application cost. Hydromulch with seeds have also the possibility of introducing invasive plants into the ecosystems and increase the costs. For large and inaccessible areas the aerial hydromulch can reduce the costs.

5. Natural and human environment

5.1 Climate

Annual rainfall
  • < 250 mm
  • 251-500 mm
  • 501-750 mm
  • 751-1,000 mm
  • 1,001-1,500 mm
  • 1,501-2,000 mm
  • 2,001-3,000 mm
  • 3,001-4,000 mm
  • > 4,000 mm
Agro-climatic zone
  • sub-humid

Thermal climate class: temperate

5.2 Topography

Slopes on average:
  • flat (0-2%)
  • gentle (3-5%)
  • moderate (6-10%)
  • rolling (11-15%)
  • hilly (16-30%)
  • steep (31-60%)
  • very steep (>60%)
  • plateau/plains
  • ridges
  • mountain slopes
  • hill slopes
  • footslopes
  • valley floors
Altitudinal zone:
  • 0-100 m a.s.l.
  • 101-500 m a.s.l.
  • 501-1,000 m a.s.l.
  • 1,001-1,500 m a.s.l.
  • 1,501-2,000 m a.s.l.
  • 2,001-2,500 m a.s.l.
  • 2,501-3,000 m a.s.l.
  • 3,001-4,000 m a.s.l.
  • > 4,000 m a.s.l.

5.3 Soils

Soil depth on average:
  • very shallow (0-20 cm)
  • shallow (21-50 cm)
  • moderately deep (51-80 cm)
  • deep (81-120 cm)
  • very deep (> 120 cm)
Soil texture (topsoil):
  • medium (loamy, silty)
Topsoil organic matter:
  • high (>3%)
If available, attach full soil description or specify the available information, e.g. soil type, soil PH/ acidity, Cation Exchange Capacity, nitrogen, salinity etc.

Soil texture is medium (sandy-loam)
Soil fertilits is high
Topsoil organic matter is high (forest soil)
Soil drainage/infiltration is poor-medium
Soil water storage capacity is low

5.4 Water availability and quality

Ground water table:

5-50 m

Availability of surface water:


Water quality (untreated):

for agricultural use only (irrigation)

Comments and further specifications on water quality and quantity:

Water quality (untreated) is for agriculutral use only (surface water)

5.5 Biodiversity

Species diversity:
  • low
Comments and further specifications on biodiversity:

Forest plantation

5.6 Characteristics of land users applying the Technology

Market orientation of production system:
  • mixed (subsistence/ commercial)
  • commercial/ market
Off-farm income:
  • > 50% of all income
Relative level of wealth:
  • poor
  • average
Individuals or groups:
  • employee (company, government)
Indicate other relevant characteristics of the land users:

Population density: < 10 persons/km2
Annual population growth: < 0.5%
40% of the land users are average wealthy.
60% of the land users are poor.
Market orientation of production system: subsistence (self-supply), mixed (subsistence/ commercial, commercial/ market

5.7 Average area of land used by land users applying the Technology

  • < 0.5 ha
  • 0.5-1 ha
  • 1-2 ha
  • 2-5 ha
  • 5-15 ha
  • 15-50 ha
  • 50-100 ha
  • 100-500 ha
  • 500-1,000 ha
  • 1,000-10,000 ha
  • > 10,000 ha
Is this considered small-, medium- or large-scale (referring to local context)?
  • large-scale

Average area of land owned or leased by land users applying the Technology: 2-5 ha, 5-15 ha, 15-50 ha

5.8 Land ownership, land use rights, and water use rights

Land ownership:
  • individual, not titled

5.9 Access to services and infrastructure

  • poor
  • moderate
  • good
  • poor
  • moderate
  • good
technical assistance:
  • poor
  • moderate
  • good
employment (e.g. off-farm):
  • poor
  • moderate
  • good
  • poor
  • moderate
  • good
  • poor
  • moderate
  • good
roads and transport:
  • poor
  • moderate
  • good
drinking water and sanitation:
  • poor
  • moderate
  • good
financial services:
  • poor
  • moderate
  • good

6. Impacts and concluding statements

6.1 On-site impacts the Technology has shown

Socio-economic impacts


wood production

Water availability and quality

water availability for livestock


Socio-cultural impacts

SLM/ land degradation knowledge


Improved livelihoods and human well-being

Comments/ specify:

Livelihoods and human well-being (eg education, health) are not changed by the use of Hydromulching.

Ecological impacts

Water cycle/ runoff

water quantity


surface runoff


groundwater table/ aquifer




soil moisture


soil cover


soil loss


soil crusting/ sealing

Biodiversity: vegetation, animals

invasive alien species

Comments/ specify:

If hydromulching is with seeds, it can introduce invasive species

6.2 Off-site impacts the Technology has shown

downstream flooding


damage on neighbours' fields


damage on public/ private infrastructure


6.3 Exposure and sensitivity of the Technology to gradual climate change and climate-related extremes/ disasters (as perceived by land users)

Gradual climate change

Gradual climate change
Season increase or decrease How does the Technology cope with it?
annual temperature increase well

Climate-related extremes (disasters)

Meteorological disasters
How does the Technology cope with it?
local rainstorm well
local windstorm well
Climatological disasters
How does the Technology cope with it?
drought well
Hydrological disasters
How does the Technology cope with it?
general (river) flood not known

Other climate-related consequences

Other climate-related consequences
How does the Technology cope with it?
reduced growing period well

6.4 Cost-benefit analysis

How do the benefits compare with the establishment costs (from land users’ perspective)?
Short-term returns:


Long-term returns:

neutral/ balanced

How do the benefits compare with the maintenance/ recurrent costs (from land users' perspective)?
Short-term returns:


Long-term returns:

very positive


Hydromulch is seen as a very expensive treatment without clear advantages at the short term, but good at the long term period.

6.5 Adoption of the Technology


Comments on spontaneous adoption: The technology has not been applied by any land user. It is a newly research-developed technology.

There is no trend towards spontaneous adoption of the Technology

Comments on adoption trend: The owners are not aware because of the costs, but they will change if the government start funding it.

6.7 Strengths/ advantages/ opportunities of the Technology

Strengths/ advantages/ opportunities in the land user’s view
It will prevent sediment movement and accumulation over roads and down slope properties and values at risk.

How can they be sustained / enhanced? By developing more economic application formulations and schemes.
Strengths/ advantages/ opportunities in the compiler’s or other key resource person’s view
It is a technology that has the advantages of the mulching technique and also can be used as a tool for increase the biodiversity, expand the distribution of some protected plant species at the same time that soil is keep in place.

How can they be sustained / enhanced? The use of longer mulch fibers can still increase the hydromulch effectiveness, since some researchers found the longest fibers to be more effective in soil erosion control than the shorter ones.

6.8 Weaknesses/ disadvantages/ risks of the Technology and ways of overcoming them

Weaknesses/ disadvantages/ risks in the compiler’s or other key resource person’s view How can they be overcome?
Hydromulch is very expensive when compared to straw mulch, but not more effective in post-fire soil erosion reduction. To develop hydromulch mixtures using the lowest amount of water as well as other chemical components to the minimum.
Some researchers found very low performance due to the interception of the hydromulch jet by the dead standing trees Verify when applying it that the ground coverreach a minimum of 60%
Sometimes the mulch component (wood fibers, chopped paper) can be removed very easily by heavy rainfall, and thus treatment effectiveness can decrease greatly.

7. References and links

7.1 Methods/ sources of information

7.2 References to available publications

Title, author, year, ISBN:

EFFECTIVENESS OF HYDROMULCHING TO REDUCE RUNOFF AND EROSIONIN A RECENTLY BURNT PINE PLANTATION IN CENTRAL PORTUGAL. Prats et al. (in press). Land Degradation and Development DOI: 10.1002/ldr.22362-Effects of hydromulch on post-fire erosion and plant recovery in chaparral shrublands ofsouthern California. Hubbert et al. 2012 International Journal of Wildland Fire 21:155–167.Rough D. 2007. Effectiveness of rehabilitation treatments in reducing postfireerosion after the Hayman and Schoonover fires, Colorado FrontRange. Fort Collins, CO: Colorado State University. MsC. Thesis; 186.Robichaud PR, Ashmun LE, Sims BD. 2010. Post-fire treatment effectivenessfor hillslope stabilization. General Technical Report, RMRS-GTR-240. U.S. Department of Agriculture, Forest Service, Rocky Mountain ResearchStation, Fort Collins, CO.

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